Abstract
Purpose:
Glaucoma is known to be a multifactorial disease comprising intraocular pressure (IOP) and ocular hemodynamics. Analysis of the optic disc has been proposed as one aspect for the classification of glaucoma. According to previous reports, the retinal vascular caliber related with ocular hemodynamics is narrow in normal tension glaucoma (NTG) patients. The purpose of this study was to examine the retinal vascular caliber and ocular perfusion pressure in regard to the Nicolela’s classification of optic disc types in NTG patients.
Methods:
This observational study involved 52 untreated NTG patients (24 males and 28 females; mean age: 50.8±12.9 years) and 52 healthy controls (24 males and 28 females; mean age: 53.7±8.6 years), comparable for age and sex who were seen at the Kyoto Prefectural University of Medicine Hospital and the Oike-Ikeda Eye Clinic, Kyoto, Japan. Patients with a treatment history, except for dry eye disease or allergic conjunctivitis, were excluded from the study. Based on width data of the 6 largest venules and 6 largest arterioles in a digital retinal image, we calculated the central retinal artery equivalent (CRAE) and the central retinal vein equivalent (CRVE) and AV ratio (AVR) by IVAN software kindly provided by the University of Wisconsin-Madison using the Parr-Hubbard-Knudtson formula. Ocular perfusion pressure (OPP) was estimated using blood pressure and IOP measurements. NTG patients were categorized into four groups [Focal Ischemic (FI), Myopic (MY), Senile Sclerotic (SS), and Generalized Enlargement (GE)] according to the Nicolela’s classification of optic disc types by four independent glaucoma specialists.
Results:
CRAE, CRVE, AVR, and OPP were 127.9μm, 186.1μm, 0.69, and 43.7mmHg, respectively, in the NTG group, and 134.9μm, 200.0μm, 0.68, and 50.3mmHg, respectively, in the control group. CRAE, CRVE, and OPP were significantly lower in the NTG group than in the control group (p<0.01, respectively). The NTG group consisted of 15 FI, 18 MY, 5 SS, and 14 GE patients. CRAE was narrower in SS, CRVE was narrower in MY, SS, and GE, and OPP was lower in MY and GE significantly than in the control group (p<0.05, respectively).
Conclusions:
Retinal vessels were narrow and OPP was low in NTG patients, and ocular hemodynamics may be different among NTG patients from the aspect of the classification of optic disc.